The heterogeneity of HLA-B44 is confirmed and the sequence difference between the two major subtypes, B*4402, *4403, is attributed to one polymorphic site in the third exon. A method is described to discriminate B*4402 and B*4403, and the occurrence and linkage disequilibrium of B*44 subtypes is discussed. No example of B*4401 polymorphism in exon 2 was observed.